The revelation that a pair of twins had inadvertently married raises questions about the attraction of siblings who suffer separation and how the IVF explosion could lead to more such cases

Imagine what they thought, imagine the turmoil they endured. They are the twins who, it emerged on Friday, were separated at birth and given up for adoption only to meet by chance years later - and marry.

The man and woman, unaware that they were brother and sister, had grown up separately, perhaps far apart, in different families. Yet when fate brought them together again, they experienced an uncanny bond and a sexual attraction.

As Lord Alton, who revealed the case, said: "They were never told they were twins. They met later in life and felt an inevitable attraction."

Did they sense some blood relationship? It certainly must have seemed odd: both had been born on the same day in the same year. Did they just take that as an incredible, happy coincidence? Did they not know they were adopted? Or did they suspect they were related, only for the power